You leave the cord attached to the baby, and the placenta to the cord, until it falls off. It's called lotus birth. Apparently newborns are quite fond of their placentas, having had them for a plaything for 9 months, who can blame them.
Lulu, I think she just wanted to keep the placentas as they were 'part of her babies' or something like that. And where else to keep them but buried in your garden? As they didn't have a garden of their own, they had to use my parent's garden. Don't think my dad was too impressed!